Defense Date

2020

Document Type

Thesis

Degree Name

Master of Science

Department

Environmental Studies

First Advisor

Salvatore Agosta

Abstract

Invasive species exist in nearly every ecosystem both terrestrial and aquatic. Improving our understanding of the mechanisms that shape the ability of these organisms to physiologically cope with their surroundings will be crucial to preparing for future impacts of climate change. The Gypsy Moth (Lymantria dispar) has been expanding its range across North America over the last 100+ years since its arrival in Medford, Massachusetts. This study quantifies upper thermal limits (UTL) across 8 different populations of L. dispar in North America and seeks to determine if signals of local adaptation to climate across a latitudinal gradient may be present. Upper thermal limits for each population were determined through the use of a temperature controlled water bath and involved both acute and extended heat exposure to quantify thermal tolerance. Results from linear regression analysis and generalized linear modeling of the temperature ramping trials indicated that UTL values for each population were highly correlated with 30 year annual and seasonal temperature averages, as well as latitude. Linear and logistic regression analyses of the soak trial data showed no statistically significant relationships between percent population survival at 43°C and 30 year seasonal/annual temperature averages, latitude, weight or elevation. Although the soak results were not significant, the trends from this analysis were generally in the same direction as those observed in the ramp analysis. Based on the results of the ramp trial analysis we conclude that the UTL of third instar L. dispar larvae is closely related to climate and that potential signals of localized adaptation to climate are present, which is consistent with our hypothesis. It may be possible that thermal performance in general for L. dispar is undergoing selection and thus is shifting UTL with it or that direct selection may be occurring on upper thermal tolerance specifically. If this is indeed the case then we can expect this invasion to be altered in response to changes in thermal tolerance.

Rights

© The Author

Is Part Of

VCU University Archives

Is Part Of

VCU Theses and Dissertations

Date of Submission

8-4-2020

Available for download on Wednesday, August 04, 2021

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